HELP WHITE DOT.......

[tristar]

Hi I'm new, I present on this forum, do not know if this post is in the right place, if not so I apologize.
I have been given recently one vectrex (European Version). No power goes the famous white dot on the screen. I have changed the four main capacitors and I have reviewed all the welds of the plate. Even so I still have the same problem, no sound.
Any help is welcome.
Thank you very much.

[sj]

Might be too obvious but I gather you have twiddled the knob on the back of the unit?

[tristar]

Yes i play with this know but only obtain brightness.

[centaura]

It´s only a hypothesis but this fault could be induced by the AY3-8912 IC itself:
"this IC is responsible for the sound output, controller input and graphic output within the Vectrex console and other vintage computer systems"

[binarystar]

this might help www.youtube.com/watch?v=hvHITP14oRg

[kokovec]

Do you hear the intro music? If so then it might not be the sound chip.
Could be the MUX, DAC or any of the components that drive the CRT.
Changing out the caps on the power board might help. I just revived my Vectrex that way.
Unfortunately sometimes it requires an oscilloscope and some luck.

[tristar]

I can't hear any sound, and change the four principal caps, but still have the white dot. i clean all chips, and put it back again,





AY3-8912 IC this is a transistor or what kind of component?.


thanks folks.

[centaura]

AY3-8912 is the sound chip.
It connects with other components like the DAC (digital to analog) chip or the controller input.
The microprocessor interfaces with peripheral devices and external signals through the PIA (Peripheral Interface Adaptor). One of the two PIA ports interfaces the micro with the sound chip I/O and the DAC, so if these chips are dirty or worn all the system could be affected (image, sound and controller input)

I said it´s only a hypothesis, reading your vectrex signs..
I hope you can find an expert or any more of light in that, and revive your machine.

[vectrexmad]

This is from the Vectrex FAQ:

7.4) My Vectrex just shows a white dot when I turn it on. I can hear
the game playing but there is no picture. Can I fix it?


There is 1 common problem that will cause this symptom. Inside the
unit there is a 4-wire power connector connecting the side board to the
bottom board. Often units with no picture have bad solder joints on
this connector. Try resoldering the pins and see if that helps.

Doesn't explain why you can't hear the sound though.....

[klydefrog]

I'm also having this issue and started my own thread:
vectorgaming.proboards.com/thread/1034/white-sound-proper-voltage-connector

[tristar]

Finally i had change all capacitors, etc, But still have the same problem.


Now a technician determine the problem in the flyback(line transformer). Did anyone now where can i buy it?


Thanks for all.

[gauze]

if you are hearing no sounds changing the flyback will not help, that just provides high voltage to the CRT and if you have a dot already I'd say it's definitely NOT this.

[Kangsteri]

If there is not even a sound, the issue seems to be on logic board. Maby a bad ROM, sound- or other chip.

The white dot indicates that its on and working but there is no data to draw on the screen. And it may be caused by many different issues. It also depends what kind of dot it is. Is it bright or dim, and where on the screen it locates.

If its bottom of the screen and center, then its caused by broken LM379.
If its center of the screen and slightly to upper right corner. Then it might be many different things. Or even combination of different issues. Most easy way to try fix it is to clean the logic board. Then refurbish the chips if there is no shine on them anymore. They usually are oxidated to grey or even rusted. Often its not enough just to reseat them. I clean them puttind the teeth against some plate/sheet and use steel wool on it, carefully!
You should also measure all power connections to logic board (-5v, ground, +5v and 13v). And the XYZ connections to power board (9v, 9v and 0,5v).
Best way is to have other working Vectrex to change and test broken parts. If not, you just need to guess and try getting new parts one by one. There is not many parts that usually fail on Vectrex. Its most likely one of the chips, or one of the transistors.

And when someone gets these fixed, its good to still take them to proper TV fixer. So the ringing can be tuned on oscilloscope and get the lines fixed straight.

[gauze]

it's definitely something on logic board I'd say but unless you see something wrong, testing can be hard unless you have some equipment, at least a logic probe or oscilloscope.

One thing to check is for clock signal on the CPU pin, this is provided by a crystal (6mhz I think?) and if it's not oscillating the CPU can't load or perform instructions. Replacing the crystal would fix that (maybe).

It's possible the CPU itself is fried, the ROM could be corrupted too I suppose? I'd have to look at schematics a little to think of other things where you'd get no sound or graphics but proper power.

Anyone up for working on a flowchart of this sort of thing?

[kokovec]

I say start by replacing the chips that are already on DIP sockets. I believe this includes the DAC which is known to fail. In fact you might want to remove the chips from their sockets and clean both the chips and the sockets with contact cleaner.
Also, look for bad solder joints on the logic board. Be careful not to heat them up too much which may lift up some of the traces.
Wires with crimp connections sometimes get corroded or loose.
By the way, make sure to discharge the CRT if you're going to be poking around in the Vectrex.

I doubt it's the flyback transformer but if it is you're toast as there are no replacements. They were custom manufactured I believe.